1. Field of the Invention
The present invention relates to a data transferring device and, more particularly, to a transferring device for transferring measured values obtained by a sensor device into a processing device for processing the measured values.
2. Prior Art
The above-mentioned sensor device is, for example, an absolute angular position sensor, by which an absolute angular position of a shaft is ascertained. The shaft can be, for example, a crankshaft or camshaft of an internal combustion engine. The measured values obtained from this type of sensor are angle values for the angular positions at which the observed shaft is oriented at respective measurement times.
When the sensor device is an absolute angular position signal generator for measurement of the angular position of the crankshaft or camshaft of an internal combustion engine, the above-named processing device is, for example, a microprocessor or a microcontroller of the control unit of the motor vehicle containing the concerned internal combustion engine. The motor vehicle control unit needs the above-named measured values of angular position for, among other things, timing the various fuel injection events.
Although there are many possible methods for reception of the measured values from an absolute angular position sensor or other sensor device into the processing device requesting these measured values and also for the manner and type of the transferring method from the sensor device to the processing device, these methods have various problems. These problems are described in the following paragraphs.
The reception of the measured values obtained by the sensor device in the processing device can occur
A1) in response to a special command from the processing device (e.g. in response to a command from a program running in the processing device), or
A2) automatically at predetermined time intervals (for example, every 10 ms).
In the first-named possibility (A1) the command normally occurs always exactly when the processing device (for example a program running in it) immediately demands the relevant information. This reception method has the advantage that the obtained information is always relatively current. Disadvantageously however the retrieval or reception of the information may be connected with a comparatively great effort. This can lead, for example, to very great demands or load on the processing device (for example if the information is required prior to each ignition event).
The second-named possibility (A2) for receiving the information in the processing device puts a comparatively reduced load on the processing device. However disadvantageously the obtained information is not always current when it is used. If the data, for example, are only read every 10 ms, the measured values may already be 10 ms delayed at the time when they are used. This can cause considerable inaccuracy when the rotating shaft whose position is being measured is rapidly rotating (e.g. a camshaft or crankshaft of an internal combustion engine driven at high speed).
Several possibilities exist for the manner and type of the transfer method for transferring the measured data picked up by the sensor device into the processing device, namely
B1) transmission of an analog signal dependent on the measured values to the processing device (voltage level corresponding to a predetermined angular position),
B2) transmission of a pulse-width modulated signal dependent on the measured values to the processing device (the angular position depends on the ratio of the high-level and low-level phases of the signal, and
B3) transmission of a digital signal dependent on the measured values to the processing device (the measured values are generally serially transferred).
The first-named possibility (B1) has the advantage that a comparatively constant time delay is present and that the transfer of the measured values into the processing device can occur according to possibility A1 and also according to possibility A2. However the required D/A and/or A/D converters have a disadvantageously large cost. Also the transfer of the measured values into the processing device is unfortunately very susceptible to interference (especially interference caused by the electromagnetic field due to the ignition events and/or the incorrect scanning of the signals).
The second possibility (B2) is very robust regarding interference and permits a comparatively simple conversion and evaluation. Generally the data transfer only takes place according to the possibility A2, so that the data are always current at the end of a period of the pulse-width modulated signal.
The third possibility (B3) is similarly very robust regarding interference. Generally here also the transfer only takes place according to possibility A2, since the information can only be input at discrete times.
It should be apparent from the above explanation that it is not currently possible to transfer measured values of this type of data into a processing device, especially data regarding the angular position of a rapidly rotating shaft of an internal combustion engine, under all circumstances and to have current or real time data always available. This is true in spite of the many possibilities for transferring measured variables obtained by a sensor device into a processing device that are currently known in the art.
It is an object of the present invention to provide an improved transfer device of the above-described kind, which suffers at least to a lesser extent from the above-described disadvantages and which transfers actual measured values into the processing device under all circumstances.
According to the invention the transfer device for transferring measured values picked up by a sensor device into a processing device that processes the measured values comprises an interface between the sensor device and the processing device, in which the measured values obtained by the sensor device at predetermined times are stored with the respective times at which these values were obtained.
By providing an interface with memory means between the sensor device and the processing device the measured values detected by the sensor device can be fed into the processing device or read by another device or coded at another later time. Since the interface not only passes the measured values to the processing device, but also the respective times at which the values were measured, the values of the measured variable between the actual measurement times or at later times may be calculated or estimated.
This has proven to be advantageous in many respects. The interface can be constructed in many ways, e.g.
so that the processing device can obtain actual or current data with a minimal effort in the desired manner and way,
so that the sensor device may be replaced with another sensor device without effecting the processor.
Advantageous embodiments are described in the following dependent claims, description and figures.